Bluetooth enhanced data rate (EDR) packet includes a Gaussian frequency-shift keying (GFSK) modulated segment and a Differential Phase-Shift Keying (DPSK) modulated segment. During modulation, both an amplitude AMP and a phase PHA are switched directly from the GFSK modulation scheme to the DPSK modulation scheme. Since GFSK and DPSK are different modulation schemes, the amplitude of the GFSK end point differs greatly from the amplitude of the DPSK starting point, and the phases of the GFSK end point and the DPSK starting point are also largely different. The above direct switching results in amplitude and phase discontinuities, which leads to a spectral leakage at the baseband. The leakage passes through a phase-locked loop (PLL) and a Power Amplifier (PA), and is finally transmitted at the Radio Frequency (RF), which leads to a deterioration of the Adjacent Channel Power Ratio (ACPR). ACPR is defined as the ratio between the total power adjacent channel (intermodulation signal) to the main channel's power (useful signal). ACPR is desired to be as low as possible. A high ACPR indicates that significant spectral spreading has occurred.